[Scons-dev] please try latest default branch

[Dirk Bächle]

On 28.01.2014 23:57, Gary Oberbrunner wrote:

> More results, no fix yet.

>

> The generated file all-defuns.c I mentioned before is definitely part 

> of the problem.  I back-ported the tracing code I wrote to just before 

> Dirk's memory optimization.  In that version, near the beginning of 

> the build phase something calls node.is_up_to_date() on all-defuns.c 

> and it says it has changed, due to depending on a dir "mkl" which is 

> in no_state (i.e. hasn't been evaluated yet).  In Dirk's version, this 

> result gets cached, which seems sensible.  But in the old version, 

> when the taskmaster considers that all-defuns.c node, and calls 

> is_up_to_date(), now it correctly returns True, because by now the mkl 

> dir has been evaluated and it's in up-to-date state.  So it's 

> definitely the caching that's causing the trouble, but I don't 

> understand why is_up_to_date should return different values at 

> different times -- especially go from false to true before anything's 

> been built.  Perhaps there's another bug in the code which Dirk's 

> patch exposes?

>

> I would think is_up_to_date() should never assume that being 

> unprocessed (i.e. no_state) means not up-to-date; I'd think it should 

> have scanned the no_state node before its dependents.  Anyone have any 

> clues?

>

>

When I implemented my changes, I saw that in the old version the 
changed() (or connected methods) could be actually called after a file 
was built. And since there was nothing cached, this could lead to 
creating additional build infos in the same step. So there was a danger 
of having a build info hash signature in the .sconsign, that would not 
actually describe how the target was built (more like, how would it be 
built next time).

Maybe your build DAG relied on this fact so far? By the way, are you 
building with "-j" or is it failing single-core too? Do you think it's 
possible to extract an isolated test case from this, now that we know 
more about what seems to happen?

Regarding the is_up_to_date() method, we're pretty much on the same page.

Dirk